Spindle checkpoint strength is dictated by the number of unattached kinetochores, cell volume and cell fate. We show that the conserved AAA-ATPase, PCH-2/TRIP13, which remodels the checkpoint effector Mad2 from an active conformation to an inactive one, controls checkpoint strength in C. elegans. Having previously established that this function is required for spindle checkpoint activation, we demonstrate that in cells genetically manipulated to decrease in cell volume, PCH-2 is no longer required for the spindle checkpoint or recruitment of Mad2 at unattached kinetochores. This role is not limited to large cells: the stronger checkpoint in germline precursor cells also depends on PCH-2. PCH-2 is enriched in germline precursor cells and this enrichment relies on conserved factors that induce asymmetry in the early embryo. Finally, the stronger checkpoint in germline precursor cells is regulated by CMT-1, the ortholog of p31^comet, which is required for both PCH-2’s localization to unattached kinetochores and its enrichment in germline precursor cells. Thus, PCH-2, likely by regulating the availability of inactive Mad2 at and near unattached kinetochores, governs checkpoint strength. This requirement may be particularly relevant in oocytes and early embryos enlarged for developmental competence, cells that divide in syncytial tissues and immortal germline cells.

主轴检查点的强度由未连接的动植物数量，细胞体积和细胞命运决定。我们显示保守的AAA-ATPase，PCH-2 / TRIP13，将检查点效应物Mad2从一种有效的构型改造为一种无活性的，控制秀丽隐杆线虫的检查点强度。。先前已经确定此功能是纺锤体检查点激活所必需的，我们证明了在经过基因操纵以减少细胞体积的细胞中，纺锤体检查点或未连接的动植物的Mad2募集不再需要PCH-2。此作用不仅限于大细胞：种系前体细胞中更强的检查点还取决于PCH-2。PCH-2在种系前体细胞中富集，这种富集依赖于在早期胚胎中诱导不对称的保守因子。最后，生殖细胞前体细胞中更强的检查点受p31^彗星直系同源基因CMT-1的调控。，这是PCH-2定位到独立的动植物和富集种系前体细胞所必需的。因此，PCH-2可能通过调节未连接的动植物处和附近的非活性Mad2的可用性来控制检查点的强度。在卵母细胞和扩大了发育能力的早期胚胎，在合胞体组织中分裂的细胞以及永生生殖细胞中，这一要求可能特别相关。